1. Field of the Invention
The present invention relates to a hybrid drive system which is equipped with two kinds of power sources of an internal combustion engine and a motor generator so that it can use one of the power sources solely or two of them together in accordance with the using condition.
2. Related Art
One example of the hybrid drive system to be used in an electric car or the like of the prior art is disclosed in JPA-3-121928. In this hybrid drive system, there are arranged in series an internal combustion engine to be operated by the thermal energy, a motor generator to be operated by the electric energy of a battery, and a transmission for converting the torque outputted from the internal combustion engine or the motor generator.
The drive shaft of the internal combustion engine, i.e., the crankshaft is connected to the motor shaft of the motor generator, which is connected to the input shaft in the transmission. Incidentally, this transmission is equipped therein with an output shaft which is connected to the input shaft through a gear train. In accordance with the running condition of the vehicle, moreover, at least either the internal combustion engine or the motor generator is driven to generate an output torque. This output torque is transmitted to and transformed by the transmission, so that the converted torque can be transmitted to the wheels thereby to select a variety of running modes.
In the hybrid drive system thus disclosed in the aforementioned JPA-3-121928, however, the internal combustion engine, the motor generator and the transmission are arranged in series. As a result, the drive shaft, the motor shaft and the input shaft are arranged on the common axis to enlarge the total length of the hybrid drive system in the axial direction. This arrangement raises the floor of the vehicle in the compartment thereby to raise such problems in the inferior mountability that the compartment space is narrowed or that the arrangement of the peripheral devices is restricted.